This invention relates to a surface illuminating device, and an image display apparatus provided with the same, such as film image reproducing apparatus and a photographed image recognizer.
In recent years, a film image reproducing apparatus and a photographed image recognizer for displaying an image utilizing a liquid crystal display panel or the like have been known. The liquid crystal display panel used in the apparatus of this kind receives illumination light from a backlight source arranged on the rear surface thereof and displays an image having a tone difference utilizing the transmission and cut-off action of the light by liquid crystal molecules aligned by an image signal and random liquid crystal molecules.
Conventionally, as a backlight source has been known a surface illuminating device which is comprised of a rectangular parallelepipedic light introducing plate mounted in a frame having reflecting inner surfaces except the upper and one side surface thereof, a fluorescent tube provided in contact with the one side surface of this light introducing plate and covered with a reflecting surface on the opposite surface, and a diffusing plate provided on the upper surface of the light introducing plate (Japanese Unexamined Utility Model Publication No. 4-40269). This surface illuminating device uniformly introduces light from the fluorescent tube to the diffusion surface by forming a gradation reflecting portion on the bottom surface of the light introducing plate. Accordingly, if the above surface illuminating device capable of emitting uniform illumination light from the front surface thereof is adopted as a backlight for the liquid crystal display panel which is an illumination object, an image can be uniformly displayed on the display panel regardless of its display position.
Further, Japanese Unexamined Patent Publication No. 7-159720 discloses an optical visually recognizer of eyeglass type in which a backlight source using a single fluorescent tube is held between a pair of opposite LCDs (Liquid Crystal Displays).
With the surface illuminating device disclosed in Japanese Unexamined Utility Model Publication No. 4-40269, if it is applied to a plurality of illumination objects, a plurality of such illuminating devices are required. This stands as a hindrance to the demand of making the apparatus smaller, thus disadvantageously leading to an increase in the cost.
On the other hand, the backlight source disclosed in Japanese Unexamined Utility Model Publication No. 7-159720 simply uses a fluorescent tube and a diffusing plate. This is effective for such a small display surface as to be installed in eyeglasses, but cannot give an effective uniform amount of light to a relatively large illumination object applied to the reproduction and recognition of an image. Further, in the case of the surface illuminating device, there is the problem of large thickness if the backlight source is used while being held between the LCDs.